حسابداری برای بهره وری از: آیا خوب است فرض کنیم که جهان کاب داگلاس است؟

The development accounting literature almost always assumes a Cobb–Douglas (CD) production function. However, if in reality the elasticity of substitution between capital and labor deviates substantially from 1, the assumption is invalid, potentially casting doubt on the commonly held view that factors of production are relatively unimportant in accounting for differences in labor productivity. We use international data on relative factor shares and capital-output ratios to formulate a number of tests for the validity of the CD assumption. We find that the CD specification performs reasonably well for the purposes of cross-country productivity accounting.

A critical decision in any development accounting analysis, which aims to decompose GDP per worker into its fundamental components (physical capital, human input and total factor productivity), is the choice of aggregate production function. The standard choice is a Cobb–Douglas (CD) specification, and the common finding is that observed differences in labor productivity cannot be adequately accounted for by differences in physical and human capital. Instead, total factor productivity (TFP) accounts for the lion’s share of observed differences in GDP per worker.

In this paper we have utilized data on capital-output ratios and labour shares to inquire whether the use of an aggregate CD production function is problematic for the purpose of development accounting. Making this assessment requires us to examine what might be a reasonable assumption for the elasticity of substitution between capital and labor (ES), when invoking a more general CES production technology. The observed lack of any clear correlation between relative shares and capital-output ratios suggest an ES close to 1. Under the assumption of Harrod neutral technological change, this is a simple yet powerful test of whether a “large” ES is plausible. The data suggest it is not. Moreover, the observed variation in factor shares is consistent with a CES production function featuring an elasticity of substitution around 0.8. The results from using a CES function with ES = 0.8, and a CD approach to development accounting are very similar.